1. Field of the Invention
The present invention relates to electron emission apparatuses and methods for making the same and, particularly, to a carbon nanotube based electron emission apparatus and a method for making the same.
2. Discussion of Related Art
Conventional electron emission apparatuses include field emission displays (FED) and surface-conduction electron-emitter displays (SED). The electron emission apparatus can emit electrons in the principle of a quantum tunnel effect opposite to a thermal excitation effect, which is of great interest from the viewpoints of promoting high brightness and low power consumption.
Referring to FIG. 8, a field emission device 300 includes an insulating substrate 302, a number of electron emission units 310, cathode electrodes 308, and gate electrodes 304. The electron emission units 310, cathode electrodes 308, and gate electrodes 304 are located on the insulating substrate 302. The cathode electrodes 308 and the gate electrodes 304 cross each other to form a plurality of crossover regions. A plurality of insulating layers 306 are arranged corresponding to the crossover regions. Each electron emission unit 310 includes at least one electron emitter 312. The electron emitter 312 is in electrical contact with the cathode electrode 308 and spaced from the gate electrode 304. When receiving a voltage that exceeds a threshold value, the electron emitter 312 emits electron beams towards an anode. The luminance is adjusted by altering the applied voltage. However, the distance between the gate electrode 304 and the cathode electrode 308 is uncontrollable. As a result, the driving voltage is relatively high, thereby increasing the overall operational cost.
Referring to FIG. 9 and FIG. 10, a surface-conduction electron-emitter device 400 includes an insulating substrate 402, a number of electron emission units 408, cathode electrodes 406, and gate electrodes 404 located on the insulating substrate 402. Each gate electrode 404 includes a plurality of interval-setting prolongations 4042. The cathode electrodes 406 and the gate electrodes 404 cross each other to form a plurality of crossover regions. The cathode electrodes 406 and the gate electrodes 404 are insulated by a number of insulating layers 412. Each electron emission unit 408 includes at least one electron emitter 410. The electron emitter 410 is in electrical contact with the cathode electrode 406 and the prolongation 4042. The electron emitter 410 includes an electron emission portion. The electron emission portion is a film including a plurality of small particles. When a voltage is applied between the cathode electrode 406 and the prolongation 4042, the electron emission portion emits electron beams towards an anode. However, because the space between the particles in the electron emission portion is small and the anode voltage can't be applied into the inner portion of the electron emission, the efficiency of the surface-conduction electron-emitter device 400 is relatively low.
What is needed, therefore, is to provide a highly efficient electron emission apparatus with a simple structure and a method for making the same.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one embodiment of the present electron emission apparatus and method for making the same, in at least one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.